fix(files): reject nonregular capture and JSON inputs

Verify selected files through a nonblocking opened handle before reading. Preserve regular-file symlinks and return actionable CLI/MCP diagnostics without publishing output.

Co-authored-by: YouWish <29498139+Y0UW1SH@users.noreply.github.com>

docs/javascript-application-workflows.md

@@ -175,6 +175,10 @@ All five CLI commands accept inline JSON or a path to a JSON file. The CLI
 returns an Evidence record directly. Put the full records in a later CLI input;
 a separate CLI process has no retained MCP connection state.
 
+File inputs must be regular files; symlinks to regular files are accepted.
+Directories, named pipes and device files produce an input error before JSON
+parsing.
+
 For a literal string trace, analyze your supplied tree once, then build the
 input from the saved Evidence (replace the target and seed):